An example of wireless communication is cellular wireless communication performed in the context of a cellular communications network. Cellular communication networks may comprise a plurality of cells that mobiles may communicate with, sequentially or concurrently. Due to mobility, a mobile can change from a first situation where it communicates with a first cell to a second situation where it communicates with a second cell. Such a change may be called a handover.
Handovers comprise also so-called soft handovers, where a mobile begins communicating with a new cell without ceasing to communicate with a previous cell, and softer handovers where a mobile begins communicating with a new sector of a cell it is already in communication with, without ceasing communicating with a sector it already communicates with. Handovers may be triggered by measurements conducted in mobiles, wherein a mobile may detect that it is leaving the service area of a first cell and moving toward a service area of a second cell. When a mobile reports such measurements to a serving cell, the network the serving cell is comprised in may decide to handover the mobile to the second cell.
Smart phones have become prevalent as users desire more data-centric services when on the move. Smart phones may benefit from long times of continuous connection to the network. For example, where a smart phone is programmed to serve as an email client, a smart phone may be in more or less constant communication with an email server to discover arriving email messages. Another example is internet browsing, where a smart phone may keep up a connection open for a prolonged period of time, with intermittent data traffic as the user occasionally requests new web pages to be fetched.
Optimizing the behavior of smart phones aims, among other things, to minimize the power consumption for smart phones trying to keep open always-on type of connections when connected to cellular networks. Always-on connections without active service usage may carry “keep-alive” or status update messages intermittently. An assigned connection such as, for example, a radio resource connection, RRC, connection, may be maintained for long periods of time to prevent unnecessary state transitions between an idle mode and a connected mode between packet transmissions.
In order to minimize power consumption during prolonged periods of assigned connections, a mobile may be programmed to enter a discontinuous mode, wherein the mobile is able to reside partly in a low-power mode and only “wake-up” periodically to maintain the connection. In discontinuous mode a mobile may also be able to monitor for incoming data from the network, for example for a mobile-terminated call. One example of such a mode is a discontinuous reception, DRX, mode, where a mobile may monitor a control channel from a base station only intermittently, according to a time pattern known to both mobile and base station. When residing in a low-power phase in DRX mode, a mobile may have its radio receiver in an inactive mode to conserve energy.